Re: 16-bit gray PNG write broken?

Posted by G. Jehle on
URL: http://imagej.273.s1.nabble.com/16-bit-gray-PNG-write-broken-tp3695138p3695140.html

Quoting Wayne Rasband <[hidden email]>:

> On Sep 9, 2008, at 1:48 PM, G. Jehle wrote:
>
> > Hi everyone,
> >
> > I'm running ImageJ 1.39u on Ubuntu GNU/Linux (x86_64).
> >
> > Whenever I try to save a simple '16-bit grayscale' image
> > as PNG, ImageJ saves a '8-bit/color RGB' image instead.
> >
> > I generated a 16-bit gray PNG using Matlab.
> > Opening the PNG in ImageJ; works just fine with ImageJ
> > recognizing the file as 16-bit gray, all values look ok.
> >
> > However, using 'File > Save As > PNG...' on the very
> > file just opened results in a '8-bit/color RGB' PNG to be
> > saved.
> >
> > Any ideas to why this might happen?
>
> ImageJ 1.41d and later saves 16-bit and 32-bit images as 8-bit PNGs.
> Earlier versions saved as RGB. ImageJ converts to 8-bits when saving in
> PNG format so that the images are more likely to display correctly in
> other applications. Save in TIFF format if you need to preserve 16-bit
> or 32-bit values.

Thanks for the info wayne.

Although I have to say that, IMHO, this is bad.
Changing bit depth without giving a warning, even more so
in a case where the image format actually supports the higher
bit depth is very, very misleading and a source for error and frustration.

Are there any considerations for future versions of ImageJ
to make this behavior optional?
I'd really like to use 16-bit grayscale PNG.

Where can I submit a bug report? (I'm serious)

> -wayne
>


//
Best regards,

G. Jehle

HTWG Konstanz - University of Applied Sciences
Fakultät Informatik

HTWG Konstanz
Fakultät Informatik
Brauneggerstraße 55
D-78462 Konstanz
www.htwg-konstanz.de